Self-pumped phase conjugation is observed using a KNbO3 crystal. The reflectivity of an external ring phase conjugate mirror is measured as a function of temperature for 515 nm radiation. The maximum reflectivity is 26% at 124 °C. On cooling, the reflectivity decreases and vanishes completely below 62 °C. The phase conjugate nature of the retroreflected beam is illustrated. The temperature-dependent response time is shown to be proportional to (T-56 °C)-1.